Magnavox Sound distorted

The sound was just find until I used the AV plugs on the front. Now the sound is perfectly find as long it's on the AV channel and something is pluged into the av. However I also noticed only the AV channel shows that it is on Stereo. The other channels are on stereo but they still show as mono. There is sound but even on full volume it's it's sounds like it's only on level 3-4. If anyone have any idea's
I'd appreciate hearing them. Thanks Rani